Polishing Tool, Polishing Head, Polishing Apparatus, And Polishing Method

Abstract

A polishing tool for polishing a workpiece by holding a polishing material between the workpiece and its polishing surface, the polishing tool including: a main shaft part that has the polishing surface at a front end and that extends along a polishing axis; a plurality of elastic parts that are continuous from the main shaft part and that extend radially outward; and a plurality of seat parts that are continuous to the radially outside of the plurality of elastic parts. A position at which the main shaft part connects to each of the elastic parts and a position at which the corresponding seat part connects thereto are different in a direction of the polishing axis.

What is claimed is: 
     
         1 . A polishing tool for polishing a workpiece by holding a polishing material between the workpiece and a polishing surface of the polishing tool, the polishing tool comprising:
 a main shaft part that has the polishing surface facing the workpiece at a front end and that extends along a polishing axis, the polishing axis being a virtual axis defined as a direction in which a center of the polishing surface approaches or moves away the workpiece;   a plurality of elastic parts that are continuous from the main shaft part and that extend in a radially outward direction with respect to the polishing axis; and   a plurality of seat parts that are continuous to a radially outside of the plurality of elastic parts, wherein   a position at which the main shaft part connects to each of the elastic parts and a position at which the corresponding seat part connects to each of the elastic parts are different in a direction of the polishing axis, and   when the respective seat parts are applied with equal amounts of displacement toward a same side that is either a radially inside or radially outside by a tool driving mechanism, the plurality of elastic parts elastically deform and the main shaft part is displaced so as to include an axial component with respect to the polishing axis, whereas   when the respective seat parts are applied with different amounts of displacement toward the same side that is either the radially inside or radially outside, or the displacement toward different sides that are the radially outside and the radially inside by the tool driving mechanism, the main shaft part is displaced so as to include a radial component with respect to the polishing axis.   
     
     
         2 . The polishing tool according to  claim 1 , wherein the plurality of elastic parts and the plurality of seat parts are disposed at equal intervals in a circumferential direction with reference to the polishing axis. 
     
     
         3 . The polishing tool according to  claim 2 , wherein the number of the elastic parts and the number of the seat parts each are three. 
     
     
         4 . A polishing head having the polishing tool according to  claim 1 , the polishing head comprising:
 a tool base; and   a tool driving mechanism that is disposed on the tool base to displace or elastically deform the polishing tool, wherein   the tool driving mechanism includes a plurality of driving units that are disposed in the plurality of seat parts to radially displace the seat parts.   
     
     
         5 . The polishing head according to  claim 4 , comprising a tool control device that controls the tool driving mechanism, wherein
 the tool control device includes a first frequency signal generator that generates a plurality of first frequency signals to periodically reciprocate and displace the plurality of driving units so that increase-decrease cycles of displacement amounts coincide with each other.   
     
     
         6 . The polishing head according to  claim 5 , wherein:
 the tool control device further includes
 a second frequency signal generator that generates a plurality of second frequency signals to periodically reciprocate and displace the plurality of driving units so that the increase-decrease cycles of the displacement amounts coincide with each other, and 
 a signal superimposing unit that generates driving signals for the respective driving units by superimposing the plurality of first frequency signals and the plurality of second frequency signals, wherein: 
   the plurality of first frequency signals generated by the first frequency signal generator coincide with each other in increase-decrease phase; and   the plurality of second frequency signals generated by the second frequency signal generator are different from each other in increase-decrease phase.   
     
     
         7 . The polishing head according to  claim 5 , wherein:
 the tool control device further includes
 a second frequency signal generator that generates a plurality of second frequency signals to periodically reciprocate and displace the plurality of driving units so that the increase-decrease cycles of the displacement amounts coincide with each other, and 
 a signal superimposing unit that generates driving signals for the respective driving units by superimposing the plurality of first frequency signals and the plurality of second frequency signals, wherein 
   the first frequency signals have a frequency higher than the frequency of the second frequency signals.   
     
     
         8 . The polishing head according to  claim 5 , comprising a bias signal generator that generates a bias signal to be superimposed on at least one of the first frequency signals. 
     
     
         9 . The polishing head according to  claim 8 , comprising a polishing head setting calculation unit that varies the bias signal generated by the bias signal generator by referring to scanning path information for the polishing surface regarding the workpiece and/or shape information on the workpiece. 
     
     
         10 . The polishing head according to  claim 1 , wherein the tool driving mechanism vibrates the polishing surface along a spiral moving locus. 
     
     
         11 . The polishing head according to  claim 10 , wherein the tool driving mechanism displaces a spiral axis of the spiral moving locus on the polishing surface. 
     
     
         12 . A polishing apparatus, comprising:
 a base;   the polishing head according to  claim 4 ;   a polishing head holding mechanism that is provided on the base to hold the polishing head;   a workpiece holding mechanism that is provided on the base to hold the workpiece; and   a relative movement mechanism that relatively moves the workpiece and the polishing head in an axial direction of the polishing axis and in a radial direction with reference to the polishing axis.   
     
     
         13 . A polishing method for polishing a workpiece by holding a polishing material between a polishing surface of a polishing tool and the workpiece, the polishing material containing abrasive grains dispersed in a fluid, the polishing method comprising:
 disposing a plurality of driving units along a circumferential direction with reference to a polishing axis to cause each of the driving units to displace a contact point with the polishing tool in a radial direction with reference to the polishing axis, the polishing axis being a virtual axis defined as a direction in which a center of the polishing surface approaches or moves away the workpiece;   generating a synchronization frequency signal to periodically reciprocate and displace the plurality of driving units so that increase-decrease cycles and increase-decrease phases of displacement amounts coincide with each other;   generating a plurality of first frequency signals to periodically reciprocate and displace the plurality of driving units so that the increase-decrease cycles of the displacement amounts coincide with each other;   generating driving signals for the respective driving units by using at least the plurality of first frequency signals; and   displacing the plurality of driving units by the plurality of driving signals so as to displace the polishing surface of the polishing tool in an axial direction and a radial direction with reference to the polishing axis.   
     
     
         14 . The polishing method according to  claim 13 , wherein:
 a plurality of second frequency signals are generated to periodically reciprocate and displace the plurality of driving units so that the increase-decrease cycles of the displacement amounts coincide with each other;   the plurality of first frequency signals coincide with each other in increase-decrease phase and the plurality of second frequency signals are different from each other in increase-decrease phase;   the driving signals for the respective driving units are generated by superimposing the plurality of first frequency signals and the plurality of second frequency signals; and   the plurality of driving units are displaced by the plurality of driving signals so as to displace the polishing surface of the polishing tool in the axial direction and the radial direction with reference to the polishing axis.   
     
     
         15 . The polishing method according to  claim 13 , wherein:
 the driving signals for the respective driving units are generated by superimposing a bias signal on at least one of the first frequency signals; and   the plurality of driving units are displaced by the plurality of driving signals so as to displace the polishing surface of the polishing tool in the axial direction and the radial direction with reference to the polishing axis.   
     
     
         16 . The polishing method according to  claim 15 , wherein the bias signal is varied by referring to a scanning path information for the polishing surface regarding the workpiece and/or shape information on the workpiece. 
     
     
         17 . The polishing method according to  claim 13 , wherein the polishing surface is vibrated along a spiral moving locus. 
     
     
         18 . The polishing method according to  claim 17 , wherein a spiral axis of the spiral moving locus on the polishing surface is displaced. 
     
     
         19 . A polishing method for polishing a workpiece by holding a polishing material between a polishing surface of a polishing tool and the workpiece, the polishing material containing abrasive grains dispersed in a fluid, the polishing method comprising:
 disposing a plurality of driving units along a circumferential direction with reference to a polishing axis to cause each of the driving units to displace a contact point with the polishing tool in a radial direction with reference to the polishing axis, the polishing axis being a virtual axis defined as a direction in which a center of the polishing surface approaches or moves away the workpiece;   generating frequency signals that are at least twice as many as a number of the driving units;   inputting a driving signal to each of the driving units, the driving signal being obtained by superimposing at least two frequency signals among the frequency signals; and   displacing the plurality of driving units by the plurality of driving signals so as to displace the polishing surface of the polishing tool in an axial direction and a radial direction with reference to the polishing axis.